THESIS
2017
xviii, 120 pages : illustrations (some color) ; 30 cm
Abstract
Graphene as a two-dimensional material has attracted more and more interests due to its
remarkable properties. Nowadays chemical vapor deposition (CVD) on Cu foil is the most
popular method to achieve large area, high quality and layer number controllable graphene
films. The understanding of the graphene/Cu interaction is not only important for successful
graphene transfer onto other applicable substrates but also for tuning the growth behavior
during the synthesis step. In this PhD thesis, we first investigated the decoupling process of
graphene from Cu foil by oxidation-assisted water intercalation. Our findings reveal that the
decoupling process initiates from the graphene edges and defect sites, assisted by interfacial
copper oxidation and water intercalation due to Cu galva...[
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Graphene as a two-dimensional material has attracted more and more interests due to its
remarkable properties. Nowadays chemical vapor deposition (CVD) on Cu foil is the most
popular method to achieve large area, high quality and layer number controllable graphene
films. The understanding of the graphene/Cu interaction is not only important for successful
graphene transfer onto other applicable substrates but also for tuning the growth behavior
during the synthesis step. In this PhD thesis, we first investigated the decoupling process of
graphene from Cu foil by oxidation-assisted water intercalation. Our findings reveal that the
decoupling process initiates from the graphene edges and defect sites, assisted by interfacial
copper oxidation and water intercalation due to Cu galvanic corrosion. During this process,
interfacial oxidation acts as the dominating role. In the second part, we established a facile
strategy to control the graphene nucleation by tuning the gas flow rate and restricting gas
diffusion in semi-open space. In addition, by applying the Cu/quartz substrate, the
dehydrogenation of carbon precursor is greatly enhanced leading to boosted graphene growth
rate while not affecting the nucleation density. With this method, sub-centimeter sized single
crystal graphene grains can be obtained in one hour. Finally, we demonstrated that epitaxial
graphene growth on copper can be achieved by simply turning off hydrogen during the growth.
We find that the graphene grains grown on both Cu (111) and Cu (110) align in one orientation,
while two orientations with ~30° rotation are obtained on Cu (100). This epitaxial growth is
achieved due to stronger edge interaction between graphene and Cu substrate. On the other
hand, the more surface oxygen modifies the growth mechanism from attachment limited to
diffusion limited resulting in non-hexagonal grain shapes.
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